I am curious about the motor and control technology. So-called "brushless DC", which always looks to me like an electronically-commutated permanent-magnet rotor motor?

The motor configuration you describe is the standard type of spindle motor / drive arrangement used in pretty well all modern CNC machines. Not a recent development by any means, as I was installing / commissioning such drives over 20 years ago (from Fanuc & Indramat mainly) & the company I worked for then were not at the "cutting edge" of the industry – brushed DC drives were cheaper & frequently had performance characteristics better suited to the older machines that we retrofitted.

The brushless syncronous motors tend to have a higher base speed (the cross-over point from constant torque to constant power operation) than brushed DC equivalents, but also a greated constant power speed range (not subject to brush commutation limits). From memory, DC brushed motors with field weaking drives had a constant power / base speed ratio of around 3 or 4:1, where syncronous motors were 6/8:1. So for a syncronous motor with a base speed of 1500 rpm (typical), that would give a maxiumum speed of 9000 rpm (6:1 ratio).

The brushless motors also have the advantage that the windings are in the stator & can be cooled externally (air or liquid) , where brushed DC motors have both stator (field ) windings and a wound armature & require the cooling air to be blown through the motor – always a problem where coolant or oil mist is present. They are also cheaper to make – wound armatures with commutators are expensive.

Nigel B